This is a study of the determinants of postpartum amenorrhea in Bangladesh. The length of the amenorrheic period is an important parameter of fertility in Bangladesh because it accounts for a large percentage of the birth interval. Although the extended lengths of amenorrhea have previously been documented, reasons for this phenomenon have been speculative. Specific elements of the study will focus on delineating which factors are responsible for the extended lengths of amenorrhea. Specifically, we will examine the relationship of nutrition and breast-feeding patterns on amenorrhea. Other issues to be assessed include the seasonality of return of menses, and seasonal variations in occupational activities, diet, and frequency of illnesses as they relate to the return of menses postpartum.